The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the invention relate to a disconnectable mooring system for a vessel, comprising a mooring buoy member and a turret structure mounted in a moonpool of the vessel, the mooring buoy member being anchored to the seabed and having a plurality of passages each adapted to receive a riser, the turret structure having a receptacle for receiving the buoy member and locking device for locking the buoy member in the receptacle, the turret structure accommodating a plurality of conduits to be connected to risers installed in passages of the buoy member, wherein the turret structure is rotatably supported in the moonpool of the vessel by means of at least a bearing assembly mounted above sea level.
A disconnectable mooring system of this type is disclosed in GB-A-2 285 028. In this known mooring system, the mooring buoy member is provided with a centering projection to be received in a receiving entry of the receptacle of the turret structure. This construction requires a relatively accurate prepositioning of the buoy member and the receptacle during a mooring or connection operation. Further, the conduits accommodated in the turret structure need to be aligned with the risers of the buoy member before locking the buoy member in the receptacle. The conduits are terminated in the receptacle by movable sleeves which can be retracted within the receptacle to protect the sealing rings during connecting or disconnecting the buoy member. The movable sleeves need to be sealed with respect to the stationary conduits, resulting in a more complex and vulnerable construction.
In the disconnectable mooring system according to GB-A-2 285 028, the receptacle of the turret structure is located at the level of the vessel keel, wherein all engaging faces of the conduits, receptacle, risers and buoy member are located outside of the turret structure. Inspection of the engaging faces and sealings is impossible when the buoy member is at its location in the receptacle.
U.S. Pat. No. 4,604,961 discloses a disconnectable mooring system for a vessel, wherein the buoy member is provided with a conical outer casing which is received in a turret with a corresponding conical shape. This known mooring system only allows to the connection of one central riser with one central conduit mounted in the moonpool of the vessel. The bearing assembly rotatably supporting the turret in the moonpool is located below sea level. Further, the buoy member supports the locking device for locking the buoy member in the receptacle. This means that the bearing assembly and locking device with its operating mechanism are continuously exposed to the seawater environment.